Gas measuring device



latentecl Nov. 10, 1953 UN lTED STATES PATENT OFFItE 2,658,385 GAS MEASURING DEVICE Robert D. Richardson, Michis' a'n City, link, as-

sign-or to The Hays'Corpoi-athmMichigan City,

Ind, a corporation of Indiana Application Italy '23, 194i, sensible. "762,963

8 Claims.

This invention relates to improvements in gas measuring devices, and more particularly to devices for measuring the oxygen content of a gas sample.

The device utilizes the principle that the para= magnetic properties of oxygen are high compared to all other gases except NO. The tie-- vice is of the comparison type, having two test chambers of similar characteristics "provided with similar electric thermal elements arranged therein. The onIy difference between the two "comparison chambers is in the rovision n che of said chambers of means for creating a heterogenous magnetic field. A device of this type is illustrated and described in my co'epending patent application, Ser. 595,569, filed Ma 24, 1945.

This invention has for its primary object the provision of a device of this character of 'increased sensitivity and accuracy which is re 'sponsive to minute differencesor changes in the oxygen content of a gas sample and which pro"- vides an improved or increased electrical output for a given percentage of oxygen content being measured, as compared to the output of previous devices ntiliaing the same operating principle.

A further object is to provide a device of this character having a test cell constructed to 1ncrease the cooling effect of the flow of oxygen past a thermal element which is arranged in a 'hetero'genous magnetic field to induce said flow.

A further object is to provide a device of this character having a novel test cell wherein the cooling effect of oxygen on a thermal el'ementin a magnetic field is substantially uniform throughout the full extent of said element. 7 I

A further object is to provide a device of this character wherein a thermal element and ma netized pole pieces are so arranged and located in a test chamber for a gas having an oxygen content to be measured that a novel and highly effective flow of gas content to cool the thermal element is obtained. v H

other objects will be apparent from the follow ing specification.

In the drawing: I

Fig. 1 is a vertical sectional view or the device with parts illustrated diagrammatically.

Fig. 2 is a transverse horizontal view taken on line 2-'2 of Fig. 1.

Fig. 3 is an enlarged perspective view illustrating the construction and relation of the heating element and the magnetic pole pieces.

Fig. 4 is a still further enlarged transverse sectional detail view taken on line 4-4 of Fig. 3.

Referring -to the draw-m which illustrates the preferred embodiment of the invent-ion, the nul'nra-l I-ll designates a test cell which preferably constitutes; block of brass or other hon-ferrous inaterial. The material of which "cell "I0 is constreet-ed is preferably selected for its thermal stability and genera-1 ruggedness. A longitudinal passage 12 extends t rough the cell which may be formed or multiple parts, and a gas inlet conduit [4 is -c'on'n'ecte'ii. at one end of said passage 12, and a gas outlet conduit 1c is connected at the opposite end of the passage l2. The gas outlet conduit F6 may be omitted in certain instances. The passage 12 is formed in the cell adjacent one margin thereof, and a l a'i-r of substantially similar chambers 1 8 and '20 are "formed spaced relation within the cell, preferably extending paralieitg each other and perpendicular to the passage 1'2 with which each 00th.. muni'cates at one end. in one form found well suited for the ur oses (If the invention, the chambers I 8 and 20 are formed of approximately inch diameter. V H W g The cell ID has a pair of inwardly tapering elongated slots -22 ro-n ned in opposite sides thereof and communicating with the chamber it in diametrically opposed rela'tion. hese slots each mount an iron pole piece insert '24 or sunstantialiy the shape and construcnon shown in 3, thatis, substantially wedge shaped form. "Ihe'se members are suitably secured within the slots of the test cell and preferably have their outer surfaces terminating flus with the side waus 'Of the test 'cen, "as Shown in Fig. 2. The pole pieces 24 are constructed of such size and dimensions that the tips '26 thereof project into the chamber [8, as best illustrated in Fig. 2, and in one preferred form the tips of the magnets are spaced apart approximately of an inch, being blunt at their inner 'o'r confronting faces. It Will be Observed, therefore, that when the pole pieces extend for the major portion of the length 0f the chamber l8, as illustrated in Fig. '1, they form ribs "or restrictions projecting 'interi'orly into said chamber and dividing the same into two substantially similar portions hav-- ing a restricted gap ror communication there"- between. The chamber '21] is preferably provided with non-ma netic inwardly projecting ribs of the'same dimension as the pole tips 2's in chamber [8.

A permanent magnet '2t 'preferably cf (i-shape as shown in Fig. 2, and having inturned confronting pole portions 30 spaced apart a distance substantially e ual to the width of the test cell I0, cooperates with the pole pieces 24. The magnet may be provided with projecting pins 32 parallel to the pole portions adapted to pivotally mount the magnet so that the faces of its pole portions may travel in a plane parallel to the side faces of the test cell I0. It will be understood that the faces of the pole portions 30 of the magnet are so spaced that they have clearance with the side faces of the test cell sufficient to permit pivotal movement of the magnet about the pins 32 without interference or binding. Thus the magnet serves in its operative position illustrated to magnetize the pole pieces 24 when oper atively positioned or may be swung to a position clear of said pole pieces, whereby the same are substantially demagnetized.

The test cell has a pair of socket openings 34 formed therein in alignment and in communication with the inner end of each of the chambers I8 and 20. in the device. The element 36 constitutes a measuring element and is positioned in chamber I8. An element 38 constitutes a comparison element and is positioned in chamber 20. The two heating elements are similarly constructed and preferably have substantially the same heating properties. The construction of the heating elements is best illustrated in Figs. 3 and 4. A support 48 is formed of electrical insulating material, such as glass, and may be of cup shape as shown. The support 40 is mounted in one of the openings 34 in the test cell in communication with the correlated chamber thereof, said supports serving to seal and close the openings 34 in which they are mounted. A wire stem 42 extends longitudinally through the support 48 in which it is fixedly secured. The upper portion of the stem 42 projects above the support 40 to provide a terminal 44. The lower portion of the stem 42 projects below the support 40 and supports a glass tube or sheath 46 which is melted in place therearound. A coil of wire 48 is connected to one end of the stem 42 and is wound around the sheath 46 of the stem 42. The entire unit so formed is then glazed with glass of the same type used for the sheath 46 to provide an outer coat or sheath 50. A second wire stem 52 extends longitudinally through and is anchored to the support 40 in spaced relation to the stem 42. The upper end of stem 52 projects above the support 40 to provide a terminal 54. The lower end portion of the stem 52 is secured to the glazed coat 50, whereby it cooperates with the stem 42 to support the depending heater unit in desired position with relation to the support 40. The coil 48 is connected at its upper end to the stem 52 and at its lower end to the stem 42. The length of the depending heater portion of each heating element is preferably such that it extends substantially the full length of that one of the chambers I8 and 20 in which it is positioned, as best shown in Fig. l. The two heating elements 36 and 38 are preferably positioned centrally within their associated chambers I8 and 20, respectively, and the heating element 36 preferably extends parallel to and between the confronting faces of the tips of the pole pieces 24, as illustrated in Figs. 2 and 3. In one form of the device in which the spacing of the magnets is approximately 1% of an inch, a heating element of .025" diameter was used, positioned substantially equi-spaced from the confronting tip faces of the pole pieces and between the same, said top faces being A" wide.

The terminals 44 and 54 of the two heater ele- Two heating elements are provided L ments are connected in separate legs 68 and 62 of a Wheatstone bridge circuit Whose remaining legs 64 and 66 have balanced impedances or resistances 68 interposed therein. The bridge circuit is connected to any desired source of power I0, which may be either direct current or alternating current, by lead I2 connected to point I4 between the legs 60 and 64 of the bridge, and by lead I6 connected to point I8 of the bridge between the legs 62 and 66. A lead is connected to the bridge at point 82 between the legs 60 and 62, and a lead 84 is connected to the bridge at point 86 between the legs 64 and 66. The two leads 80 and 84 are connected to a device 88 which is to be operated, which device may be either a recorder or an indicator and which preferably, in the case of the recorder at least, is provided with a suitable amplifier.

In the operation of the device, the gas to be tested is supplied by the conduit I4 and discharged thereby into the passage I2. The oxygen content of this gas is attracted into the heterogeneous magnetic field surrounding the heating element 36 in the chamber I8 by reason of the paramagnetic properties of the oxygen. As the gas comes into contact with or within the thermal influence of the heating element 36, it is heated by said element. The heating of the oxygen causes it to lose its attraction to the magnetic field. Consequently, the comparatively cool oxygen from passage I2 continually displaces the heated oxygen in the area in the chamber I8 immediately adjacent the heating element 36 and a net flow of gas is maintained. Gas from the passage I2 likewise enters the chamber 20 and is heated therein in the same manner but without the influence of a magnetic field.

By virtue of the properties of oxygen in a magnetic field, that is, the attraction of cool oxygen to a magnet and the loss of such attraction upon heating thereof, the rate of flow of gas in the chamber I8 and along the heating element 36 is greater than the rate of flow in the chamber 28 around the heating element 38 thereof. This increased gas flow serves to cool the heating element 36 somewhat, thereby changing the electrical value of the heating element 36 compared to the same value of the element 38 and unbalancing the normally balanced bridge circuit to permit operation of the recorder or other instrument 88 in direct proportion to the percentage of oxygen present in the gas sample. If there is no oxygen present in the system to be influenced by the magnetic field, the flow of gas in the two chambers I8 and 20 will be the same, and the two heating elements 36 and 38 operate in balanced relation.

The arrangement and shape of the chamber I8, the pole pieces 24 and the substantially coex tensive relation of the pole pieces with respect to the heating element positioned therebetween are important features of this invention. This arrangement insures that substantially the full length of the heating element 36 will be within and subject to the direct influence of the magnetic field. Consequently, the gas flow and its cooling action upon the heating element is substantially uniform throughout the full length of the heating element, thereby producing a greater effect, considered electrically, than in my previous device. In other words, the measurable electrical effect, when comparing the two heating elements 36 and 38, is great, thus affording a greater unbalance of the bridge for any given percentage of oxygen in the gas, thereby increasing the sensitivity of the device, making measurement of small changes in oxygen percentage possible, and in general improving very materially the stability, sensitivity and accuracy of the device. In one embodiment of the invention more than 60 millivolts unbalance at the bridge was obtained, as between the two heating elements 36 and 38, for a sample of air. This is much greater unbalance than has been obtainable by previous devices, and it will be apparent, therefore, that as the percentage of oxygen in a gas sample is reduced compared to the percentage of oxygen in air, there still remains a substantial range between zero millivolts and 60 millivolts for measurable and distinct unbalance proportional to the existing oxygen content of the gas sample being measured.

It is interesting also to note that in a construction of this character the gas attracted into the magnetic field is caused to swirl transversely in the chamber, as illustrated by the arrow in Fig. 2. lhis combined longitudinal and transverse flow of gas in the test chamber produces a substantial cooling effect upon the heating element 36 which has been described and which produces the enhanced cooling effect. Such swirling action occurs through substantially the fully length of the chamber, due to the location of the magnets to extend substantially the full length of said chamber and substantially coextensive with the length of the heating element, as best seen in Fig. 3.

The provision of the ribs 2| in the chamber 20 insures that the dimensions and shape of the chamber 25! will be the same as the dimensions and shape of the chamber l8. The ribs are preferably formed of brass or some non-magnetic material which has substantially the same heat transfer properties as the iron of pole pieces 24. Consequently, the same cooling efiect inherent in the structure as a result of the formation of the parts from heat conducting material is assured, and the only difference in the cooling action is the result of the increased flow of gas around and with respect to the heating element resulting from the magnetic properties of the oxygen content of the gas. It will be understood, however, that the use of the ribs 2! is optional and not essential inasmuch as the balance of the bridge can be effected to compensate for any difference in the cooling action of the parts of the block upon the two heating elements.

While the preferred embodiment of the invention has been shown and described herein, it will be understood that changes may be made within the scope of the appended claims without departing from the spirit of the invention.

I claim:

1. In a gas measuring device, a test cell formed of non-magnetic material, said cell having a gas passage and a pair of chambers communicating with said passage, a pair of similar elongated rigid electric heating elements each projecting into one of said chambers, each of said chambers having a longitudinally extending portion of reduced transverse dimension in which one of said elements is positioned, the reduced dimension longitudinal portion of one chamber being magnetizable, the other chamber being of such size and volume and having a heating element so located therein that the heat transfer which occurs therein balances the heat transfer which occurs in the first chamber when not magnetized, inserts carried by said cell and formed of ma- -terial defining a magnetic flux path projecting into said one chamber to define said reduced dimension, and means for creating a magnetic field in and between said last named inserts, said inserts being substantially coextensive with the length of the element juxtaposed thereto.

2. In a gas measuring device, a test cell formed of non-magnetic material, said cell having a gas passage and a pair of chambers communicating with said passage, a pair of similar elongated rigid electric heating elements each projecting into one of said chambers, one of said chambers having a pair of elongated magnetizable ribs projecting therein and parallel to and in substantially diametrically opposed relation to the heating element in said chamber, and means for creating a magnetic field around'said last named element along the major portion of its length, the other chamber having a crosssectional size and a relation to said heating element such that a heat transfer occurs therein similar to the heat transfer occurring in the first chamber when not magnetized.

3. In a gas measuring device, a test cell formed of non-magnetic material and having a gas passage and a pair of chambers communicating with said passage, a pair of magnetizable members carried by said cell and projecting into one of said chambers to terminate in spaced confronting relation. said members extending substantially the full length of said chamber, and a pair of similar heating elements carried by said cell and each projecting into one of said chambers, one of said elements being positioned substantially parallel to and between the confronting portions of said members.

4. In a gas measuring device, a test cell formed of non-magnetic material and having a gas passage and a pair of chambers communicating with said passage, a pair of magnetizable members carried by said cell and projecting into one of said chambers to terminate in spaced confronting relation, said members extending substantially the full length of said chamber, and a pair of similar rigid electric heating elements carried by said cell and each projecting into one of said chambers, one of said elements being positioned substantially parallel to and between the confronting portions of said members, the projecting portions of said members tapering inwardly and said heating element being spaced therefrom a small distance compared to its spacing from the remaining surfaces of said chambers.

5. In a gas measuring device, a test cell formed of non-magnetic material and having a gas passage and two elongated chambers communicatmg with said passage, one chamber comprising parallel elongated cavities open at one end at said passage and communicating for substantially the full length thereof through a restricted gap, inserts formed of magnet-fiux-transmitting material carried by said cell and projecting into said chamber to define said restricted gap, an elongated rigid electric heatin element in each chamber, said elements being comparable, the element in said last named chamber being positioned in said gap, and means for subjecting said inserts to magnetic flux and for creating a magnetic field in said gap, the other chamber having a size and arrangement such as to produce a heat transfer balancing the heat transfer occurring in the first chamber when no magnetic flux occurs in said first chamber.

6. In a gas measuring device, a test cell formed of non-magnetic material and having a gas passage and two elongated chambers communicating with said passage, one chamber comprising parallel elongated cavities open at one end at said passage and communicating for substantially the full length thereof through a restricted gap, inserts formed of magnet-flux-transmittin material carried by said cell and projecting into said chamber to define said restricted gap, an elongated rigid electric heating element in each chamber, said elements being comparable and each including spaced juxtaposed leads connected at one end the element in said last named chamber being positioned in said gap, and means for creating a magnetic field in said gap, said field being oi substantially uniform strength throughout the length of said gap, the other chamber being of such size. shape and relation to its contained heating element as to produce heat transfer therein corresponding to heat transfer occurring in said first chamber.

7. In a gas measuring device, a test cell formed of non-magnetic material and having a gas nassage therethrough and two elongated chambers therein open only at said passage, an elongated rigid electric heating element fixedly carried by said cell and extending substantially full length in each chamber, and means for creating a magnetic field around at least the major portion of the element in one of said chambers, said last named chamber having inwardly projecting longitudinal ribs defining a cross-sectional shape adapted to cause gas having an oxygen content to move therein in a combined longitudinal and transversely swirling motion in substantially proportional response to the effect of said magnetic field upon the oxygen content of the gas, said heating element being positioned between and substantially equally spaced from said ribs.

8. The construction defined in claim 3 wherein the other chamber has a pair of non-magnetizable projections extending therein and similar in size, shape and location to the magnetizable members in said first chamber.

ROBERT D. RICHARDSON.

References Cited in the tile 01 this patent UNITED STATES PATENTS Number Name Date 1,860,544 Krueger et al. May 31, 1932 2,269,850 Hebler Jan. 13, 1942 FOREIGN PATENTS Number Country Date 712,762 Germany Oct. 24, 1941 724,041 Germany Aug. 17, 1942 60,881 Denmark May 3, 1943 64,957 Denmark Oct. 28, 1946 71,454 Norway Dec. 30, 1946 

